This disclosure relates to an active flow control device for a nacelle inlet of a turbofan engine. In particular, the disclosure relates to controlling the boundary layer at the nacelle inlet with the active flow control device.
Engine nacelle design for large commercial geared turbofan engines is a significant contributor to overall engine performance and operability. Inlet lip thickness and diffuser length associated with the fan nacelle are typically sized to provide laminar inlet flow to the engine during take-off, low speed climb, high angle of attack operation and in extreme crosswinds. As a general rule, thicker inlet lips and longer diffuser lengths are required to maintain acceptable performance at these operating conditions and minimize the potential for boundary layer flow separation. Larger inlet nacelle geometry adds size, weight and cost to the engine, which are undesirable.
Larger inlet nacelle geometry is also required to accommodate acoustic treatments to meet low noise requirements for direct drive turbofan engines. Acoustic treatments typically are not necessary for geared turbofan engines due to the decreased noise associated with their operation as compared to direct drive turbofans. Larger inlet nacelle geometry also increases overall aircraft drag at cruise operating conditions, which results in higher overall fuel burn rates and higher aircraft operating costs.
What is needed is a smaller fan nacelle that is able to maintain desired boundary layer flow at the nacelle inlet.